[FFmpeg-devel] ODML index and ticket #3531

[Michael Niedermayer]

On Thu, Apr 24, 2014 at 11:06:47AM -0400, Don Moir wrote:
> 
> ----- Original Message ----- From: "Don Moir" <donmoir at comcast.net>
> To: "FFmpeg development discussions and patches" <ffmpeg-devel at ffmpeg.org>
> Sent: Thursday, April 24, 2014 12:14 AM
> Subject: [FFmpeg-devel] ODML index and ticket #3531
> 
> 
> >referring to avidec.c
> >
> >In read_braindead_odml_indx you have this to add index entries:
> >
> >...
> >           if (last_pos == pos || pos == base - 8)
> >               avi->non_interleaved = 1;
> >           if (last_pos != pos && (len || !ast->sample_size))
> >               av_add_index_entry(st, pos, ast->cum_len, len, 0,
> >                                  key ? AVINDEX_KEYFRAME : 0);
> >...
> >
> >for a video stream ast->sample_size is always zero it appears. In fact it is set to zero
> >
> >static int avi_read_header(AVFormatContext *s)
> >{
> >   ...
> >           switch (tag1) {
> >           case MKTAG('v', 'i', 'd', 's'):
> >               codec_type = AVMEDIA_TYPE_VIDEO;
> >
> >               ast->sample_size = 0;
> >               break;
> >   ...
> >}
> >
> >So it seems its a bug to check blindly for ast->sample_size == 0 (!ast->sample_size) in read_braindead_odml_indx.
> >
> >Seems sample_rate is only valid for audio streams.
> >
> >http://trac.ffmpeg.org/ticket/3531
> 
> If you look at ticket 3531, you will see that it creates over 11
> million index entries for the file lake.avi. These appear to be
> completely bogus. The index ends up being larger than the file.
> 
> If I remove the check for !ast->sample_size and just check len, then
> you end with about 350 index entries and the file plays completely
> normal and opens in about 2 seconds. Without this, it can appear to
> be hung for a very long time.
> 
> Not sure if this is the correct thing to do though. Appears there is a lot of zero len values for the file.
> 
> ...
>            if (last_pos == pos || pos == base - 8)
>                avi->non_interleaved = 1;
> -            if (last_pos != pos && (len || !ast->sample_size))
> +            if (last_pos != pos && len)
>                av_add_index_entry(st, pos, ast->cum_len, len, 0,
>                                   key ? AVINDEX_KEYFRAME : 0);
> ...

applied that
seems not to break anything i tried

thanks

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

You can kill me, but you cannot change the truth.
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